请问高手在仿真过程中又遇到一个错误提示:<BR> Subsystem3/Sum4' computed at time 0 is Inf or NaN. There may be a singularity in the solution. If the model is correct, try reducing the step size (either by reducing the fixed step size or by tightening the error tolerances)<BR> 这样的问题改怎么处理?<BR> 谢谢!